1. Field of the Invention
The present invention relates to a light source or lighting device for illuminating a spatial light modulating element and further relates to an image display device having such a light source device.
2. Description of Related Art
There has been conventionally proposed an image display device having a spatial light modulating element and illuminating it by means of a light source device thereby to display an image by modulated lights transmitted through the spatial light modulating element. In this light display device, the spatial light modulating element displays a display image, while illumination light is modulated in accordance with the display image. The modulated light modulated by the spatial light modulating element forms an image through an imaging optics, for example, an image displayed on a screen.
As a light source device for the image display device, Japanese Patent Publication Laid-open No. 7-66455 discloses a light source device using a solid light-emitting element as a light source. As for the solid light-emitting element, there are light-emitting diode (LED), semiconductor laser diode (LD), electroluminescence element (EL) and so on.
In addition, as shown in FIGS. 1 and 2, there are known light source device each of which includes an integrator optical system for illuminating a spatial light modulating element uniformly. This integrator optical system is provided to homogenize the luminance distribution of illumination light emitted from the light source.
In the “fly-eye lens” integrator optical system of FIG. 1, the luminance distribution of illumination light for illuminating a spatial light modulating element 103 is homogenized since the illumination light is transmitted through fly-eye lenses 101, 102 each having a plurality of small lenses arranged therein.
Further, in the “rod” integrator optical system of FIG. 2, the luminance distribution of illumination light is homogenized since the illumination light is transmitted through a prismatic-shaped rod 104 repeating internal reflections. That is, in this rod integrator optical system, an image is formed on one end face (i.e. incident surface) of the rod 104. Instead, the light source 105 is attached firmly to the end face of the rod 104. In operation, light emitted from the light source 105 is propagated in the rod 104 while making internal reflections (total reflection) in the rod 104, and subsequently emitted to an outside through the other end face (or an exit end face) of the rod 104. By producing an image of the exit end face of the rod 104 on the spatial light modulating element 103 as an object to be illuminated, illumination light can be provided with a uniform luminance distribution advantageously.